One of the primary goals of wireless communication is to maximize the data rate while simultaneously making efficient use of the available spectrum. There are three primary methods of modulating a sine wave radio carrier; one of which is referred to as phase shift keying. Phase shift keying is a type of digital modulation which translates digital binary data (1's and 0's) into phase shifts on a carrier wave. For example a binary phase shift keyed (BPSK) system will transmit a particular sinusoidal signal to indicate a binary 1 and transmit the same sinusoid 180 degrees out of phase to indicate a binary 0. These two modulated waves would be referred to as the two BPSK “symbols”. This type of modulation can transmit more information during every symbol by allowing more discrete phase states (e.g. 0, 90, 180, and 270 degree phase shifts instead of just 0 and 180). For instance, having four possible phase shifts in the transmitted sinusoid provides four different symbols; transmitting twice as much information per symbol (i.e. can transmit two bits per symbol as there are now 4 different symbols to transmit). Phase shift keying is a very common type of modulation that is used in many applications including cellular phones, wireless modems, military systems, satellite communications, and many more applications.
With the introduction of cognitive radios, software defined radios, and other similar systems; it is desirable to detect the modulation of a received signal without having prior knowledge of the signal. Current cognitive radios either detect modulation based on brute force methods of trying various demodulations schemes until one works or by using a lookup table to determine what the signal should or might be at a certain frequency. The first method is not computationally efficient and the second method is not dynamic and adaptable to new signals. Methods that accomplish the same result as this invention are computationally inefficient and require knowledge of the signal's data rate to create a signal to compare it to.
This new innovative solution allows for any PSK signal to be quickly categorized by the type of PSK modulation or determined to not be PSK modulated. This is done in a computationally efficient manner. Traditional methods use covariance or correlation to detect against a known signal, but these methods are limited by the stored signals used for comparison and require knowledge about the data rate of the signal. This new innovative method can successfully detect PSK signals with any data or symbol rate without prior signal knowledge in a computationally efficient means.
In view of the above, there is a need for simplified, efficient method for determining if a signal is a PSK type signal and if so its respective characterization.